Abstract
GDSL lipase (GLIP) plays a pivotal role in plant cell growth as a multifunctional hydrolytic enzyme. Herein, a cotton (Gossypium hirsutum L. cv Xuzhou 142) GDSL lipase gene (GhGLIP) was obtained from developing ovules and fibers. The GhGLIP cDNA contained an open reading frame (ORF) of 1,143 base pairs (bp) and encodes a putative polypeptide of 380 amino acid residues. Sequence alignment indicated that GhGLIP includes four enzyme catalytic amino acid residue sites of Ser (S), Gly (G), Asn (N) and His (H), located in four conserved blocks. Phylogenetic tree analysis showed that GhGLIP belongs to the typical class IV lipase family with potential functions in plant secondary metabolism. Subcellular distribution analysis demonstrated that GhGLIP localized to the nucleus, cytoplasm and plasma membrane. GhGLIP was expressed predominantly at 5–15 day post anthesis (dpa) in developing ovules and elongating fibers, measured as mRNA levels and enzyme activity. Ectopic overexpression of GhGLIP in Arabidopsis plants resulted in enhanced seed development, including length and fresh weight. Meanwhile, there was increased soluble sugar and protein storage in transgenic Arabidopsis plants, coupled with the promotion of lipase activity. Moreover, the expression of cotton GhGLIP is induced by ethylene (ETH) treatment in vitro. A 1,954-bp GhGLIP promoter was isolated and expressed high activity in driving green fluorescence protein (GFP) expression in tobacco leaves. Cis-acting element analysis of the GhGLIP promoter (pGhGLIP) indicated the presence of an ethylene-responsive element (ERE), and transgenic tobacco leaves with ectopic expression of pGhGLIP::GFP-GUS showed increased GUS activity after ETH treatment. In summary, these results suggest that GhGLIP is a functional enzyme involved in ovule and fiber development and performs significant roles in seed development.
Highlights
Upland cotton (Gossypium hirsutum L.) is a vital economic crop worldwide, and cotton seeds and fibers are among the most important materials for the oil and textile industry
Based on the homologous plant GDSL lipase (GLIP) protein sequences, a phylogenetic tree constructed using the neighbor-joining (NJ) method showed that the GLIP proteins can be divided into four groups, and GhGLIP belongs to clade IV (Fig 2) with putative roles in plant secondary metabolism
The GLIP gene has been studied in model plants such as Arabidopsis and GDSL lipases include conserved sequence features forming the typical motifs that are responsible for various functions within the classification of four common subfamily of clades I-V, with major roles in plant development and morphogenesis of clade I, stress response of clade II, biotic response of clade III and plant secondary metabolism of clade IV [18]
Summary
Upland cotton (Gossypium hirsutum L.) is a vital economic crop worldwide, and cotton seeds and fibers are among the most important materials for the oil and textile industry. Many factors affect ovule and fiber development, including sugar biosynthesis, lipid metabolism, the plant hormone ethylene, etc. Several fatty acid biosynthesis-related genes promote ovule and fiber development by enhancing cellular fatty acid content [6,7,8,9]. Promoter fragment of the Gossypium hirsutum GDSL (GhGDSL) lipase/hydrolase gene showed stage-specific high activity and was regulated by transcription factor GhMYB1 to involve in secondary cell wall biosynthesis of fiber development [28]. We obtained a GDSL lipase gene GhGLIP that was expressed predominantly in developing ovules and elongating fibers, with the encoded protein localizing in the nucleus, cytoplasm and plasma membrane. We conclude that cotton GhGLIP may be involved in ovule and fiber development and promote seed growth
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